The long term survival of the cancer patient is determined by the probability of metastatic spread and subsequent recurrence of the disease. The metastatic progression of a breast carcinoma is not likely determined by random colonization. The proliferation of a metastatic tumor requires a significant and complex induction capacity to construct the vascular and connective tissue framework which serves the neoplasms survival and progression. It is likley that these are not random events but rather depend on specific and predeterminable characteristics of a patient and her tumor. Under support of this grant, we have with the active participation of our clinical community and within the framework of our cancer center, organized a long range breast cancer prognostic study which aims at the detailed biological characterization of large numbers of human, primary breast tumors and the host factors which may be correlated with the tumor's development and metastatic progression. These include detailed studies of the patient and her tumor with respect to their immunological, cell surface, endocrinological, virological and physiological properties. Ultimately, the prognostic efficacy of these tumor and host characteristics will be determined by the incidence of recurring tumors in the patient population under study. Intermediate evaluation for purposes of experimental monitoring and design is served by the availability of pathologic criteria, which with varying degree of certainty, can predict a tumor's aggressiveness. The precise characterization and long-term observation of the neoplastic cell population and host variables in a large number of patients under coordinated medical management may well contribute the information for a major improvement in breast cancer diagnosis and treatment. Further, it offers potential for an elucidation of the mechanisms which underlie the metastatic process.